Wind power is considered one of the cleanest, most environmentally friendly energy sources presently available, and wind turbines have gained increased attention in this regard. A modern wind turbine typically includes a tower, generator, gearbox, nacelle, and one or more rotor blades. The rotor blades capture kinetic energy from wind using known foil principles and transmit the kinetic energy through rotational energy to turn a shaft coupling the rotor blades to a gearbox, or if a gearbox is not used, directly to the generator. The generator then converts the mechanical energy to electrical energy that may be deployed to a utility grid.
Conventional rotor blades typically include a shell formed from two shell halves coupled together along corresponding edges of the rotor blade. The shell halves and, thus, the shell are relatively lightweight and have insufficient structural properties (e.g., stiffness and strength) to withstand the bending moments and other loads exerted on the rotor bade during operation. Thus, the shell is typically reinforced using a spar assembly consisting of a pair of opposed spar caps and a shear web extending perpendicularly between the opposed spar caps. This conventional spar configuration generally provides a rotor blade with a relatively high, constant stiffness.
To ensure that wind power remains a viable energy source, efforts have been made to improve the overall performance of wind turbines by modifying the size, shape and configuration of wind turbine rotor blades. One such modification has been to aero-elastically tailor rotor blades in order to take advantage of the bending and/or twisting that occurs on a rotor blade during operation of wind turbine. However, to fully appreciate such advantages, aero-elastically tailored rotor blades generally require a support structure that is capable of shedding the aerodynamic loads acting on the blade. Unfortunately, conventional spar assemblies are poor at providing the proper load alleviation needed to accommodate such loads.
Accordingly, there is a need for a spar assembly that can provide the increased load alleviation needed for aero-elastically tailored rotor blades.